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Get Ready for Dahlias: Planting Tips and Tricks! 

Get ready for dahlia season in hardiness zones 7 and below! It's almost time to watch those tubers break through the soil and transform into beautiful blooms. However, with chilly nights still lingering, like the recent 35-degree night in central Washington State, it's wise to exercise caution. Unless you have a well-protected site or plan to start indoors, it's best to wait until after Mother’s Day to plant. Keep an eye on the weather forecast, ensuring soil temperatures reach a minimum of 60 degrees both day and night before planting.

To help you prepare, here are some basic guidelines for growing dahlias:

Optimal Conditions for Growing Dahlias:

  • Locate a spot with at least 6 hours of direct sunlight daily for robust growth.

  • Ensure the soil has excellent drainage to prevent waterlogging, which can cause root rot.

  • Consider planting dahlias alongside other dahlias for mutual benefits and optimal growth.

Soil Preparation Tips for Successful Dahlia Planting:

  • Ensure thorough tilling of the soil, even if done by hand.

  • Add compost to the planting site, but avoid high-nitrogen compost like chicken manure or grass-based compost sprayed with broadleaf herbicide.

  • Avoid products with timed-release materials such as Miracle Grow.

  • If using manure, opt for well-cured fresh cow manure placed in the ground in the fall or well-cured steer manure before planting in spring. Other manures are too high in nitrogen and should be avoided.

Essential Steps for Planting Dahlia Tubers:

  • Ensure the soil temperature is consistently at least 60 degrees before planting, typically around Mother’s Day.

  • Plant dahlia tubers approximately 6 inches deep and 12–24 inches apart.

  • Make sure the “eye” of the tuber is facing up when planting.

  • After planting, refrain from watering the tubers until the plant starts to show through the soil; the tuber has enough nutrients to break through on its own.

  • Avoid heavy mulch, as it can prevent the ground from warming up, which is crucial for flower growth.

Staking Your Dahlias for Support:

  • If your plants are expected to grow over 3 feet tall, it’s essential to stake them for support.

  • To avoid damaging the tubers, it’s best to stake them at planting time rather than after they’ve started growing.

Watering Tips for Healthy Dahlias:

  • Dahlias need adequate water but dislike sitting in standing water or muddy soil.

  • They may require watering 3-4 days per week, increasing as summer heat intensifies.

  • Water deeply to ensure moisture reaches the tuber roots, which are typically 8”-10” deep.

  • Deep watering may take 45-60 minutes with drip irrigation or above-ground sprinklers.

Fertilizing Guidelines for Healthy Dahlias:

  • Begin fertilizing 30 days after planting to provide essential nutrients.

  • Fertilize every 3 - 4 weeks throughout the growing season to support vigorous growth and quality flower production.

  • Opt for fertilizers with low nitrogen contents, such as 5-10-10, 10-20-20, or 4-10-7. Consider using liquid fertilizer, especially with a drip irrigation system, for efficient nutrient absorption.

Topping Your Dahlias for Better Growth:

  • Topping keeps your plants shorter and bushier, directing more energy towards flower production and encouraging longer stems.

  • Pinch off the top of the plant just above the 3rd set of leaves or when the plant reaches approximately 18” tall to promote optimal growth.

Weed Control for Dahlias:

  • Hand-weed whenever possible to avoid herbicides that can harm your dahlias.

Pest Control Tips for Healthy Dahlias:

  • Take a preemptive approach to pests by starting spraying when the stem is about 12” tall.

  • Products like Ortho, Bayer (BioAdvanced), and Monterey offer options for most pests.

  • Combat snails by applying snail bait as soon as you see your dahlia’s first stem poke through the soil, as snails are active mainly at night.

  • Look out for White Flies, which lay their eggs on the back of dahlia leaves. Use Sevin for effective control of White Flies, Earwigs, and Cucumber Beetles. Neem Oil is another option, especially for organic gardens.

Dahlias can be a stunning addition to any garden, providing vibrant colors and textures. Following these tips will help your dahlias thrive from planting to cutting, ensuring a season filled with beautiful blooms. Share your dahlia journey with us by sending pictures to, and don't hesitate to reach out with any questions.

Happy gardening!

Calvin Howe

Quail Run Dahlias

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